Method of and apparatus for continuously casting molten metal

ABSTRACT

A method of and apparatus for continuously casting molten metal into a passageway wherein coolants are directed at the molten metal not only by conduction through portions of the passageway, but also by direct contact therewith through openings in a porous belt. In one form of the invention, a trough is mounted peripherally of a casting wheel, and the metal is retained in the rotating trough by means of surface tension. The coolant applied through the openings of the belt remains in intimate contact with the molten metal even as it shrinks away from the underside of the belt and from the sidewalls of the trough. In another form of the invention, a passageway is formed between a pair of travelling porous belts and suitable side guard means.

United States Patent Nighman 1 Feb. 15, 1972 [72] Inventor:

[73] Assignee:

William Nighman, Richmond, Va.

Reynolds Metals Company, Richmond, Va.

221 Filed: Dec.29, 1969 211 Appl.No.: 888,290

[52] US. Cl ..164/87, 164/89, 164/278,

[51] Int. Cl ..B22d 11/06 [58] Field of Search ..164/82, 87, 88, 89, 273, 276,

[56] References Cited UNITED STATES PATENTS 3,536,127 10/1970 Tafel ..164/89 X Primary Examiner-Robert D. Baldwin Assistant Examiner-John E. Roethel Att0rney-Glenn, Palmer, Lyne, Gibbs & Thompson Fagg ..164/278 [57] ABSTRACT A method of and apparatus for continuously casting molten metal into a passageway wherein coolants are directed at the molten metal not only by conduction through portions of the passageway, but also by direct contact therewith through openings in a porous belt. In one form of the invention, a trough is mounted peripherally of a casting wheel, and the metal is retained in the rotating trough by means of surface tension. The coolant applied through the openings of the belt remains in intimate contact with the molten metal even as it shrinks away from the underside of the belt and from the sidewalls of the trough. In another form of the invention, a passageway is formed between a pair of travelling porous belts and suitable side guard means.

17 Claims, 6 Drawing Figures PAIENTEUFEB 15 I972 SHEET 2 BF '3 IN VENTOR.

n m M M N T W A METHOD OF AND APPARATUS FOR CONTINUOUSLY CASTING MOLTEN METAL This invention relates to a method of and apparatus for continuously casting molten metal, and more particularly to a novel method and apparatus for cooling the molten metal more rapidly and efficiently whereby the speed of casting may be increased.

Heretofore, it has been common to cast molten metal onto a continuous casting wheel such as is shown in the US. Pat. to Properzi No. 3,346,038. In accordance with this patent, molten metal is deposited in an open trough which is thereafter covered by a solid metal belt and a coolant is directed at the underside of the trough and against the exterior of the solid metal belt as the casting wheel rotates. If this apparatus is operated sufficiently slowly, the molten metal can be made to solidify or freeze, and thereafter removed from the opposite side of the casting wheel from which the molten metal was deposited.

A number of difficulties have been experienced in the operation of such a continuous casting wheel. One of these has been the difficulty in cooling the trough sufficiently rapidly in order to obtain satisfactory cooling for certain metals. As the metal freezes or solidifies, it shrinks away from the underside of the belt and away from the sidewalls of the trough whereby the cooling efficiency drops off severely as shrinkage progresses. Moreover, in order to obtain a continuous loop for the solid metal belt, it has been customary to weld the ends of the belt. Experience has shown that the life expectancy of such welded belts is extremely short, frequently in the order of from 8 to 12 hours and rarely longer than 24 hours. As a result, a considerably amount of time must be spent in replacing the belt thereby resulting in low efficiencies.

The foregoing shortcomings and limitations are effectively overcome in accordance with the present invention wherein a foraminous wire mesh belt is used to cover the open trough at the periphery of the casting wheel. Experience has shown that th high surface tension of the molten metal prevents the molten metal from flowing through the holes in the belt whereby the metal is retained in the trough even as the casting wheel rotates. More importantly, the holes in the belt permit a cooling fluid such as water or soluble oil to be directed through the openings or pores of the belt into intimate contact with molten metal in the trough even as the latter shrinks from the underside of the belt and from the sidewalls of the trough. It has been demonstrated that both very coarse and very fine wire may be used for the belt because of the high surface tension. As a result of this technique considerably more heat may be taken through the belt as compared to the amount of heat withdrawn by coolant directed to the bottom and outer sidewalls of the trough so that the speed of operation may be increased by a factor of from about 3 to 4. The wire mesh belt is interwoven so as to avoid a single discontinuity thereacross in the form of a welded section.

NOrmally water directed against molten metal such as aluminum at l,300 F. would turn to steam with such great rapidity as to create a danger of explosion. Because of the openings in the belt, the pressure from the water turning to steam prevents any large and sudden increase of pressure so as to eliminate the danger of explosion.

Since the casting wheel may be operated at higher speeds in accordance with the present invention, it is possible to cool a number of alloys of aluminum, for example, which could not be handled on prior art casting wheels which employed a solid belt. For example, aluminum alloys 5052 and 6061 as well as other magnesium and silicon alloys may be cooled efiectively in accordance with the present invention which could not be handled adequately previously.

It has also been common to cast molten metal continuously between a pair of continuously moving metal belts provided with suitable side guard means. A typical showing thereof is contained in the US. Pat. to Pond No. 2,852,821. In accordance with this patent the continuously moving metal belts are subjected to a coolant.

Once again, an inefficient cooling system is provided because the coolant does not come into intimate contact with the metal being solidified. In addition, shrinking of the metal away from the upper belt prevents even the conduction of heat from the upper belt.

It is proposed in accordance with the present invention to substitute a pair of foraminous metal belts so as to define opposed walls of a passageway into which molten metal is cast. Any suitable guide means form another pair of opposed walls in the passageway. The molten metal is retained by the foraminous metal belts by surface tension so that it makes no difference whether casting occurs vertically, horizontally or at any other convenient angle.

The inherent advantages and improvements of the present invention will become more readily apparent upon considering the following detailed description of the invention and by reference to the drawings in which:

FIG. 1 is a diagrammatic view, in elevation of one suitable casting machine to which the present invention is applicable;

FIG. 2 is a fragmentary elevational view, drawn to an enlarged scale, showing an axial cross section of the periphery of a casting wheel;

FIG. 3 is a fragmentary plan view of a wire mesh belt as seen from line 3-3 of FIG. 2;

FIG. 4 is a fragmentary plan view of another wire mesh belt also as seen from line 3-3 of FIG. 2;

FIG. 5 is a diagrammatic elevational view of another embodiment of the present invention wherein casting is effected between moving belts; and,

FIG. 6 is a cross-sectional view taken in elevation along line 66 of FIG. 5.

Referring now to FIG. 1 of the drawings, there is shown a continuous casting machine indicated generally by the numeral 10. Casting machine 10 is shown to have a lower casting wheel 12 and an upper wheel 14. Associated with the lower casting wheel 12 is a crucible 16 whose position is variable by means of handwheel 17. The crucible 16 contains molten metal and has a small pipe 18 leading therefrom through which the molten metal is conveyed from the crucible to an external trough on the lower casting wheel. Immediately after receiving the molten metal, this external trough is covered by a continuous foraminous wire mesh belt 60 is a manner to be discussed in greater detail in connection with F IG. 2.

Numeral 20 designates a main pipe which brings a coolant into the center of the casting wheel in the manner more fully shown in the Properzi US. Pat. No. 3,346,038. The lower casting wheel 12 has a guard plate 21 thereover. In order to cool the belt 60 there is provided a water manifold 22 which functions to direct a cooling fluid onto the belt 60 and through the openings thereof in a manner to be described more fully hereinafter. After the molten metal solidifies or freezes it is directed away from the casting wheel as indicated in phantom at 24.

Referring now to FIG. 2, there is shown in greater detail a peripheral portion of the lower casting wheel 12. This is shown to have a solid web member 26 and an upstanding leg or flange 28 integral with an annular wall 30 which is secured in a recess of web member 26 by means of bolt 32. The outennost projection of the web member 26 as shown at 34 forms a track together with the upstanding leg 28 and annular wall 30 into which a peripheral insert member indicated generally at 36 is deposited. Peripheral insert member 36 is shown to have relatively massive flange or leg members 38, 40 which rest on the annular wall 30 and which are retained in rigid relationship with the wheel structure by means of nut and bolt assemblies 42 and 44, respectively. The peripheral insert member 36 further includes an open trough member which comprises thin, sloping sidewalls 46 and 48 integral with a thin bottom 50.

In order to provide access for the direction of cooling fluid toward the underside of the open trough member 46, 48, 50 the annular wall 30 is provided with a series of apertures one of which is shown at 52. Coolant directed to the center of the lower casting wheel 12 by means of main pipe 20 is directed through suitable and conventional valve means to conduit 54 which leads to chamber 56. Fluid therein is controlled by the setting of nozzles 58 so as to direct a cooling fluid through cooperating apertures 52 in annular wall 30 against the underside of bottom 50 and to the exterior of walls 46, 48 of the open trough so as to cool molten metal therein by conduction from the thin walls of the trough.

The wire mesh belt indicated generally at 60 is foraminous, that is to say, it has a plurality of holes or openings 62 such as can be seen not only in FIG. 2 but also in FIGS. 3 and 4. The modified wire mesh belt in FIG. 4 is designated 60a. Each of the belts 60 and 60a are interwoven so as to avoid a single discontinuity thereacross in the form of a welded section. Water or other cooling fluid such as soluble oil is directed through one of a series of nozzles such as shown at 64 in FIG. 2 which project from water manifold 22. The coolant is directed toward the foraminous wire mesh belt 60 through the openings 62 therein and into direct intimate contact with molten metal within the, trough formed by walls 46, 48 and bottom 50 of the peripheral insert member 36.

The peripheral inset member 36 is preferably made from copper. The foraminous wire mesh belts 60 and 600 may be made from a material which will withstand the casting temperatures involved. For aluminum, for example, this will be in the order of 1,300" F. A low carbon steel being readily available is convenient for the wire mesh belts 60, 60a. Belts which have been used and found to be satisfactory have been purchased from Cambridge Wire Cloth Company in Cambridge, Maryland. One belt designated Bl44l0520 22 is seven sixty-fourths of an inch thick, has an appropriate mesh of 12, a diameter of wire of 0.0350.028 inches, a crosssectional area of 0.185 square inches per foot, a maximum working tension of 295 lb. per foot, and a weight of 1.31 pounds per square foot. Another example designated D 264- 78-2228 was five sixty-fourths of an inch thick had an approximate mesh of 23, a wire diameter of from O.(u.8-0.0l6 inches, a cross-sectional area of 0.109 square inches per foot, a maximum working tension of 105 pounds er foot and a weight of 138 pounds per square foot. Another belt found to be satisfactory is designated CB2143224 2224 is three thirty-seconds of an inch thick and has a wire diameter of 0.028-0.023 inches, a cross-sectional area of 0.237 square inches per foot, a maximum working tension of 310 pounds per foot and a weight of 2.00 pounds per square foot. The aforementioned examples are for purposes of illustration only and not to be deemed limiting in any way.

Referring to FIGS. and 6, there is shown an upper continuous foraminous belt 70 and a lower continuous belt 72 between which molten metal is cast continuously. In this form of the invention, the words upper and lower are used to describe the particular attitude of the casting apparatus shown in FIGS. 5 and 6, but since it makes no difference whether the casting occurs vertically, horizontally or any other convenient angle, the words are not used in a limiting sense. Foraminous belt 70 is entrained around a pair of pulleys 74, and foraminous belt 72 is entrained about a pair of pulleys 76.

As best seen in FIG. 6, a pair of edge dams 78 cooperate with the lower flight of belt 70 and the upper flight of belt 7.2 to define a passageway into which molten metal, such as is indicated at 90, is cast continuously. The pair of edge dams 78 are illustrated to be made of a compressible and resilient material, such as asbestos, and retained in position by guard bars 80. However, the use of compressible and resilient edge dams 78 is completely optional and any other suitable edge dams may be employed.

A plurality of upper rollers 82 and a plurality of lower rollers 84 contact belts 70 and 72, respectively, to define the geight of the passageway formed for the molten metal 90 within narrow limits to facilitate smooth operation. A series of upper manifolds 86 and a series of lower manifolds 88 direct a coolant, such as water, toward the lower flight of foraminous metal belt 70 between rollers 82 and toward the upper flight of foraminous metal belt 72 between rollers 84, respectively. A reservoir or crucible is designated in FIG. 5 by numeral 92 from which is poured molten metal into a distribution pan or tundish 94 for deposition into the passageway formed between belts 70 and 72 and edge dams 78.

As in the previous embodiment, the use of foraminous metal belts permits intimate contact of the coolant with the molten metal being solidified and also is effective in preventing explosions from occuring.

While the invention has been described with respect to casting molten aluminum, it is believed to be applicable to the casting of molten metal generally. When applying the techniques of this invention to other metals, it is necessary to utilize a mesh opening size such that the coolant is admitted while the surface tension of the molten metal is capable of maintaining the molten metal within the casting trough.

While the holes or apertures 62 in the wire mesh belt prevent explosions from occuring when using water as a coolant, it is contemplated in the practice of this invention so as to be absolutely certain of avoiding explosion, if the mesh openings are not very large, that a coolant other than water is initially directed through the openings in the porous belt. This procedure of directing a coolant other than water continues until the molten metal has partially cooled and thereafter water is directed at the foraminous belt and into contact with the molten metal. For example, one suitable coolant other than water is a soluble oil. In order to reduce adhesion of the molten metal for the belt, it is preferred to apply a smoky flame deposition of carbon onto the belt. Alternatively, mold washes such as sodium silicate or others may be used to reduce the adhesion of the molten metal for the belt. It is also contemplated that a plurality of belts may be used simultaneously in the practice of the present invention.

By using soluble oil emulsions, for example, instead of cold water as the initial coolant applied exteriorly of the wire mesh belts 60 and 60a so as to penetrate the openings therein, it becomes possible to begin cooling more slowly and then to use a cold water coolant thereafter. It should be observed that this is not possible in prior art techniques wherein the metal shrinks away from the side of the mold so that it becomes difficult to cool in this condition. Thus a shrinkage of 7 to 8 percent by volume for aluminum is common. Speeds readily obtainable from the practice of the present invention are linear speeds of 30 to 40 feet per minute versus about 10 feet per minute on existing equipment. Because the belt life is substantially longer where a wire mesh belt is'employed, there is no longer the need for frequent stops of the continuous casting machine in order toreplace a broken belt. Also, the wire mesh belt of the present invention is substantially more flexible than a solid metal belt.

While presently preferred embodiments of the invention have been illustrated and described, it will be recognized that the invention may be otherwise variously embodied and practiced.

What is claimed is:

1. An apparatus for continuously casting molten metal comprising:

a. means defining a portion of a passageway adapted to receive molten metal,

b. foraminous metal belt means cooperating to complete said passageway,

0. means for advancing said foraminous metal belt means continuously in the direction said molten metal is cast,

d. and means to supply a coolant through the openings of said foraminous metal belt means so as to solidify molten metal that is cast into said passageway,

c. said means defining a portion of a passageway being in the form of a trough and wherein said foraminous metal belt means provides a cover for said trough.

2. An apparatus for continuously casting molten metal comprising:

a. means defining a portion of a passageway adapted to receive molten metal,

b. foraminous metal belt means cooperating to complete said passageway,

1. said foraminous metal belt means having openings of a size to admit a coolant to pass therethrough but being sufficiently small to retain molten metal in said passageway by surface tension,

c. means for advancing said foraminous metal belt means continuously in the direction said molten metal is cast,

d. and means to supply a coolant through the openings of said foraminous metal belt means into direct contact with molten metal in said passageway so as to solidify molten metal that is cast into said passageway.

3. An apparatus for continuously casting molten metal as defined in claim 1 wherein said coolant is water and openings in said foraminous metal belt means permits the expansion of said water coolant as it turns to steam, thereby preventing an explosion from occurring.

4. An apparatus for continuously casting molten metal as defined in claim 1 wherein said foraminous metal belt means is in the form of a continuous belt.

5. An apparatus for continuously casting molten metal as defined in claim 4 wherein the structure of said foraminous metal belt means comprises a wire mesh interwoven so as to avoid a single discontinuity thereacross in the form of a welded section.

6. An apparatus for continuously casting molten metal as defined in claim 1 including means to supply a coolant to the exterior surfaces of said trough.

7. An apparatus for continuously casting molten metal as defined in claim 1 wherein said trough is affixed to the outer periphery of a casting wheel and said foraminous metal belt means has openings of a size to admit a coolant to pass therethrough but said molten metal is retained within said trough by surface tension.

8. An apparatus for continuously casting molten metal as defined in claim 1 wherein said coolant is water and said foraminous metal belt means has openings which permit the expansion of said water coolant as it turns to steam, thereby preventing an explosion from occurring.

9. An apparatus for continuously casting molten metal as defined in claim 1 wherein said foraminous metal belt means is in the form of a continuous belt.

10. An apparatus for continuously casting molten metal as defined in claim 1 wherein the structure of said foraminous metal belt means comprises a wire mesh interwoven so as to avoid a single discontinuity thereacross in the form of a welded section.

11. An apparatus for continuously casting molten metal as defined in claim 1 wherein said foraminous metal belt means comprises a pair of foraminous metal belts each moving in the direction of the molten metal being cast.

12. An apparatus for continuously casting molten metal as defined in claim 11 including stationary edge guiding means which form a first pair of opposed sides of said passageway and said pair of foraminous metal belts engage the upper and lower surfaces of said stationary edge guiding means to form a second opposed pair of sides of said passageway.

13. A method of cooling continuously cast molten metal comprising the steps of:

a. forming a passageway into which molten metal may be cast, 1. at least a portion of said passageway being formed by a foraminous metal belt,

b. continuously advancing said foraminous metal belt along said passageway, c. continuously casting molten metal into said passageway, d. and directing a first coolant at said foraminous metal belt so that said first coolant penetrates said foraminous metal belt thereby shaping and remaining in intimate contact with said molten metal in said passageway even as said molten metal shrinks away from portions of said passageway not formed by said foraminous metal belt during solidification. 14. A method of cooling continuously cast molten metal as defined in claim 13 wherein said first coolant is water and said foraminous belt has openings which permit the expansion of said water coolant as it turns to steam thereby preventing an explosion.

15. A method of cooling continuously cast molten metal as defined in claim 13 including the additional step of directing a second coolant at the exterior surface of the portion of said passageway not formed by said foraminous metal belt.

16. A method of cooling continuously cast molten metal as defined in claim 15 wherein said first coolant is initially a coolant other than water until said molten metal has partially cooled and thereafter directing water at said foraminous belt.

17. A method of cooling continuously cast molten metal as defined in claim 16 wherein said first coolant other than water is a soluble oil. 

2. An apparatus for continuously casting molten metal comprising: a. means defining a portion of a passageway adapted to receive molten metal, b. foraminous metal belt means cooperating to complete said passageway,
 3. An apparatus for continuously casting molten metal as defined in claim 1 wherein said coolant is water and openings in said foraminous metal belt means permits the expansion of said water coolant as it turns to steam, thereby preventing an explosion from occurring.
 4. An apparatus for continuously casting molten metal as defined in claim 1 wherein said foraminous metal belt means is in the form of a continuous belt.
 5. An apparatus for continuously casting molten metal as defined in claim 4 wherein the structure of said foraminous metal belt means comprises a wire mesh interwoven so as to avoid a single discontinuity thereacross in the form of a welded section.
 6. An apparatus for continuously casting molten metal as defined in claim 1 including means to supply a coolant to the exterior surfaces of said trough.
 7. An apparatus for continuously casting molten metal as defined in claim 1 wherein said trough is affixed to the outer periphery of a casting wheel and said foraminous metal belt means has openings of a size to admit a coolant to pass therethrough but said molten metal is retained within said trough by surface tension.
 8. An apparatus for continuously casting molten metal as defined in claim 1 wherein said coolant is water and said foraminous metal belt means has openings which permIt the expansion of said water coolant as it turns to steam, thereby preventing an explosion from occurring.
 9. An apparatus for continuously casting molten metal as defined in claim 1 wherein said foraminous metal belt means is in the form of a continuous belt.
 10. An apparatus for continuously casting molten metal as defined in claim 1 wherein the structure of said foraminous metal belt means comprises a wire mesh interwoven so as to avoid a single discontinuity thereacross in the form of a welded section.
 11. An apparatus for continuously casting molten metal as defined in claim 1 wherein said foraminous metal belt means comprises a pair of foraminous metal belts each moving in the direction of the molten metal being cast.
 12. An apparatus for continuously casting molten metal as defined in claim 11 including stationary edge guiding means which form a first pair of opposed sides of said passageway and said pair of foraminous metal belts engage the upper and lower surfaces of said stationary edge guiding means to form a second opposed pair of sides of said passageway.
 13. A method of cooling continuously cast molten metal comprising the steps of: a. forming a passageway into which molten metal may be cast,
 14. A method of cooling continuously cast molten metal as defined in claim 13 wherein said first coolant is water and said foraminous belt has openings which permit the expansion of said water coolant as it turns to steam thereby preventing an explosion.
 15. A method of cooling continuously cast molten metal as defined in claim 13 including the additional step of directing a second coolant at the exterior surface of the portion of said passageway not formed by said foraminous metal belt.
 16. A method of cooling continuously cast molten metal as defined in claim 15 wherein said first coolant is initially a coolant other than water until said molten metal has partially cooled and thereafter directing water at said foraminous belt.
 17. A method of cooling continuously cast molten metal as defined in claim 16 wherein said first coolant other than water is a soluble oil. 